Similar to the theory of yin-yang , qi was derived from ancient Chinese philosophy, which believes everything is related. In traditional Chinese medicine , qi is treated as the fundamental substance of the human body, and its movements explain various life processes. Qi in its physiological sense constitutes, replenishes and nourishes the human body. Qi is often called ¡隆茫vital energy¡隆脌 because it is believed to be the motive energy derived from the essential substance for various vital processes.

Qi is often classified according to what it acts on. For example, the heart-qi refers to the force with which the heart works and the blood circulates, so it regulates the cardiac function; the stomach-qi refers to the force with which the stomach functions, so it regulates the gastric function. The qi that maintains normal functioning for resistance against disease is called zheng-qi, which means genuine energy or body resistance. The qi that warms the body and maintains normal body temperature is called yang-qi, which is similar to the heat energy. Metabolism of materials and energy also depends on the action of qi, including metabolism of blood, fluids and other essential materials.

Qi is formed from the inhaled oxygen, the dietary nutrients, and the inborn primordial qi stored in the kidney, which may be genetically related. Qi circulates along meridians and collaterals. A healthy body requires normal circulations of qi. Health problems occur if the flow of qi is stagnated. The circulation of qi is also closely related to mental conditions. Emotional instability may cause the stagnation of qi. For example, anger may lead to dizziness, headache, distress in the hypochondriac regions, or distention in the stomach with impairment of appetite. On the other hand, the exercise of mind can help the circulation of qi, which is the purpose qigong exercise.

Qigong is an exercise to regulate the mind and breathing in order to control or promote the flow of qi. Medical qigong can be divided into two main categories: internal qigong, which is practiced by the patients themselves to preserve and promote their own health, and external qigong, which is performed by a qigong master on a person with health problems. Practicing internal qigong requires regulation of the mind, body and respiration. There are many kinds of internal qigong, some with motion and others without. Qigong can be practiced while sitting still, standing upright, or lying on the back or side. The basic requirement is to stay comfortable and relaxed.